<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>标签的关系</title>
</head>
<body>
  html标签和head标签是父子关系(包含关系)
  <hr>
  head标签和body标签是兄弟关系(并列关系)
</body>
</html>